Autoxidation of extracellular hydroquinones is a causative event for the cytotoxicity of menadione and DMNQ in A549-S cells

Nobuo Watanabe, Henry Jay Forman

研究成果: Article査読

85 被引用数 (Scopus)


Cytotoxicity of 1,4-naphthoquinones has been attributed to intracellular reactive oxygen species (ROS) generation through one-electron-reductase-mediated redox cycling and to arylation of cellular nucleophiles. Here, however, we report that in a subclone of lung epithelial A549 cells (A549-S previously called A549-G4S (Watanabe, et al., Am. J. Physiol. 283 (2002) L726-736), the mechanism of ROS generation by menadione and by 2,3-dimethoxy-1,4-naphthoquinone (DMNQ), and therefore that of cytotoxicity, differs from the paradigm. Ninety percent of H2O2 generation by both the quinones can be prevented by dicumarol, an inhibitor of NAD(P)H quinone oxidoreductase (NQO1), at the submicromolar level, regardless of the quinone concentrations. Exogenous SOD also inhibits H2O2 production at low but not high concentrations of the quinones, especially DMNQ. Thus, at low quinone concentrations, superoxide-driven hydroquinone autoxidation accounts for more than half of H2O2 generation by both quinones, whereas at high quinone concentrations, especially for DMNQ, comproportionation-driven hydroquinone autoxidation becomes the predominant mechanism. Hydroquinone autoxidation appears to occur predominantly in the extracellular environment than in the cytosol as extracellular catalase can dramatically attenuate quinone-induced cytotoxicity throughout the range of quinone concentrations, whereas complete inactivation of endogenous catalase or complete depletion of intracellular glutathione has only a marginal effect on their cytotoxicity. Finally, we show evidence that ROS production is a consequence of the compensatory defensive role of NQO1 against quinone arylation.

ジャーナルArchives of Biochemistry and Biophysics
出版ステータスPublished - 2003 3月 1

ASJC Scopus subject areas

  • 生物理学
  • 生化学
  • 分子生物学


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